Tuesday, October 24, 2006

Harmonisation: CEN and HL7

by Gerard Freriks, former chairman of CEN TC251 WG1.

(a statement of opinions, extracted from the OpenEHR e-mail list)

Harmonisation between CEN EN13606 EHRcom and HL7v2 is not taking place.

Harmonisation between CEN EN13606 plus its Archetypes and HL7v3 message artefacts is not possible.

Harmonisation between CEN and HL7 on the level of Archetypes as performed by humans using the OpenEHR Archetype Editor Tool (and therefore EHRcom part 2) is possible. This is very much needed and taking place.

Harmonisation between CEN EN13606 EHRcom and HL7v3 work on the Clinical Statement might become possible but this has to be proven.

In general, mappings are possible only when both worlds share one or more meta-models that guide the transformation/mapping.

At the archetype level, when archetypes are presented to humans, only humans are able to translate in the absence of a formal complete and accepted ontology.

Part 1 of CEN TC251 EN13606 is not the same model as the HL7v3 RIM. A mapping between the two is not possible. They are certainly not the same.

It might perhaps be possible, with some considerable effort, to create a computational mapping between Archetypes expressing CEN TC251 EN13606 part 1 and an HL7 RMIM expressing the very same standard. By the nature of the process, these meta-models can be mapped, though only partially. And extra models would be needed to deal with all possible mappings of structural HL7v3 vocabularies and elements in part 1 of the CEN Reference Model to the CEN archetypes documented in part 3.

Requirements-based standards
CEN TC251 EHRcom (and OpenEHR) is the only EHR-related standard I know that is meticulously based on a well-researched set of requirements for the EHR as published by ISO. (EHRcom is a communication standard. OpenEHR is a specification to be used in an EHR-system.)

Proof of concept: working software
CEN TC251 EN13606 EHRcom is based on more than 15 years of research in Europe and Australia. Various proof of concept studies have been performed. The most recent one is OpenEHR, it is published functional software with open source specifications. There is also interoperable proprietary software produced by OceanInformatics from Australia based on CEN TC251 EN13606 EHRcom and OpenEHR.

The Message paradigm versus the Archetype (Two Level Model) Paradigm
Any solution derived from the RIM and expressed as a message using the HL7v3 MDF method will NEVER scale, since each vendor has to write specific software for each artifact and each version. Each clinical domain will consist of many messages, and there are many clinical domains.

Any solution based on the CEN TC251 EN13606 is scalable by the fact that only one schema based on part 1 has to be implemented by the vendor, ever.

Any CEN archetype or set of archetypes assembled in a Template can be read, stored, retrieved, presented and exchanged without the need to write any software by the vendor. Therefore EN13606 and OpenEHR provide build-in scalability.

Decision support
Systems that are conformant to EN13606 EHRcom have as an additional feature that software providing decision support is able to query ALL the data stored since all data in conformant systems is presented using one uniform method without any extra programming. Plug-and-play decision support becomes possible.

CEN TC251 EN13606 EHRcom makes real Plug-and-Play semantic interoperability possible.

EN13606 EHRcom is not only becoming a European Standard and a National Standard in the various Member States of the EU; it is on its way to becoming an International ISO standard as well.

Background: The information/knowledge economy
Healthcare (like any other business) is part of the information or knowledge economy.
Phenomena enter the human mind as data.
The human transforms the data into information using expertise and knowledge.
The information is documented via statements in documents using systems such as the Electronic Healthcare Record System.

Semantic interoperability
Semantic interoperability is about documents that describe phenomena about the patient that happen, or are supposed to happen, or have happened, in the real world.

The data that is placed in any document by the healthcare provider expresses his personal view of what happened in the real world, and meta-models govern the way the healthcare provider is documenting this view.

Semantic interoperability is possible when two communicating healthcare providers share the same meta-models. Or models that can be mapped onto each other safely.

Only systems based on the same meta-model can be integrated easily. The following meta-models can be distinguished:

Meta-Model: Health Information System
E.g. CEN TC251 Health Information Services Architecture (HISA)

Meta-Model: Document
E.g. CEN TC251 EHRcom part one, HL7v3 CDA R2/3, HL7v3 Clinical Statement.

Meta-Model: Clinical Model
E.g. Archetypes and Templates as described by CEN TC251 EN13606 parts 2 and 3. Archetypes and Templates define the information model healthcare providers need to document their care where they need to share with others the salient information. Archetypes and Templates constrain a meta-model for a Document. It is because of this that Clinical Models can be transformed only when they share the same meta-model for the Document.

Meta-Model: Healthcare Provision
E.g. CEN TC251 WG2 System of Concepts for Continuity of Care. Only when healthcare providers use the same shared set of concepts that are needed to describe the provision of healthcare they are able to co-operate in the treatment of the same patient and documentation thereof.

Meta-Model: Coding Systems
In the meta-models and other models used by the healthcare providers and its EHR-system codes are used. Only when both sender and receiver (e.g. co-operating healthcare providers) use the same coding systems patient-safe exchange is possible.

Meta-Model: Semantic Links
E.g. CEN TC251 EHRcom part 3. In the various meta-models and models components will be linked with annotations. These annotations express the nature of the link between the components. Patient-safe exchange is possible when both communicating partners use the same meta-model used for describing the semantic links and the semantics of the links. The semantic links are used by the various models the EHR-system the Healthcare provider is using.

Without a (implicitly or explicitly) shared ontology, it will not be possible to populate all the models in a way that makes possible patient-safe exchange of documented information.

The Message paradigm: HL7v2 and HL7v3 Message standards fold Meta-Models (and Models) 1, 2, 3, 4 , 5 and 6 together in one set of schemas, to be uniformly implemented by all vendors.

The Archetype paradigm: CEN TC251 and OpenEHR do not fold all these Meta-Models and Models together. Vendors only need to implement the Meta-Models of 1 and 2 only once. All other models can be used without any needed implementation effort by the vendor. Thereby enabling a better, more flexible, safer and plug-and-play interoperability.


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